1. Field of the Invention
The present invention relates to an improved reaction for the isomerization between 3,4-dichlorobutene-1 and 1,4-dichlorobutene-2.
2. Description of the Prior Art
Heretofor it has been proposed to heat a dichlorobutene isomer in the presence of an isomerization catalyst of at least one metal salt of copper, iron, zinc or aluminum. However, these catalysts have relatively low catalytic activity. Therefore, it has been proposed to improve the activity of these catalysts by adding various auxiliary catalysts to the metal salts. For example, British Pat. No. 798,889 proposes the addition of an organic amine to a copper salt, Japanese Unexamined Patent Publication No. 1514/1971 proposes the addition of an organic nitrile to cupric naphthenate, Japanese Unexamined Patent Publication No. 11560/1972 proposes the addition of an organic dihydroxy compound to a salt, Japanese Unexamined Patent Publication No. 18808/1972 proposes the addition of an aniline chlorinated derivative to a salt, and Japanese Patent Publication No. 42853/1973 proposes the addition of an amine hydrochloride to cuprous chloride.
U.S. Pat. No. 3,927,130 also shows a technique for effecting the isomerization of dichlorobutene starting materials in which a catalyst of a combination of a metal compound such as cupric sulfate, cupric acetate, ferric chloride, or the like or even copper metal and an amine salt such as the hydrochloride salt of triethylamine, diethylamine, or ethylenediamine is employed.
In some studies it has been found that large amounts of by-products having high boiling points as tar are produced when an amine is added to the catalyst, and satisfactory catalytic activity can not be achieved in low concentration of the known catalysts.
It has also been found that it is necessary to use an isomerization catalyst in the reaction which has high catalytic activity and which results in lower decomposition of dichlorobutene and fewer side-reactions which form by-products having high boiling points and which is not corrosive in reaction apparatus.
The decomposition of the dichlorobutene and the formation of tar by-products of high boiling points are problems which result in decreased yields of the desired dichlorobutene isomer product and in the clogging of the reaction apparatus which shortens the operable time frame of the reaction.
Normally catalyst concentration is increased in a reaction system to increase the degree of catalyst activity. On the other hand, from the point of view of economy and recovery of the waste catalyst, it is undesirable to use greater quantities of catalyst.
Canadian Pat. No. 723,185 discloses a catalyst system which promotes isomerization reactions between 3,4-dichlorobutene-1 and 1,4-dichlorobutene-2 which consists of a combination of a cuprous salt and a halide solubilizing agent which can be a halide salt of an organic base such as morpholine hydrochloride, hexamethylenediamine dihydrochloride, hydroxylamine hydrochloride, piperidine hydrochloride or the like. However, the reaction is conducted in a water miscible organic solvent which can give rise to certain disadvantages.